U.S. patent number 7,605,207 [Application Number 12/093,566] was granted by the patent office on 2009-10-20 for flame retardant bromobenzyl systems.
This patent grant is currently assigned to Bromine Compounds Ltd.. Invention is credited to Dov Beruben, Dorit Canfi, Ron Frim, Jakob Oren, Nasif Yassin, Joseph Zilberman.
United States Patent |
7,605,207 |
Oren , et al. |
October 20, 2009 |
Flame retardant bromobenzyl systems
Abstract
Polybrominated bisaryl compounds containing bromomethyl or
bromomethylene groups are provided, as well as flameproof polymeric
formulations comprising the compounds. The novel compounds exhibit
a good thermal stability, and are particularly suitable for
flame-retarding polystyrene thermoplastic foams. A process for
making the polybrominated bisaryl compounds is also provided.
Inventors: |
Oren; Jakob (Nesher,
IL), Yassin; Nasif (Tamra, IL), Zilberman;
Joseph (Haifa, IL), Canfi; Dorit (Haifa,
IL), Frim; Ron (Haifa, IL), Beruben;
Dov (Beer Sheva, IL) |
Assignee: |
Bromine Compounds Ltd. (Beer
Sheva, IL)
|
Family
ID: |
38049071 |
Appl.
No.: |
12/093,566 |
Filed: |
November 16, 2006 |
PCT
Filed: |
November 16, 2006 |
PCT No.: |
PCT/IL2006/001327 |
371(c)(1),(2),(4) Date: |
May 29, 2008 |
PCT
Pub. No.: |
WO2007/057900 |
PCT
Pub. Date: |
May 24, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080281024 A1 |
Nov 13, 2008 |
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Foreign Application Priority Data
Current U.S.
Class: |
524/469; 524/464;
570/182; 570/184; 570/185; 570/199; 570/252; 570/254 |
Current CPC
Class: |
C07C
17/12 (20130101); C07C 17/14 (20130101); C07C
25/18 (20130101); C07C 43/225 (20130101); C07C
43/29 (20130101); C08K 5/03 (20130101); C08K
5/06 (20130101); C07C 17/12 (20130101); C07C
25/18 (20130101); C07C 17/14 (20130101); C07C
22/04 (20130101) |
Current International
Class: |
C08K
5/03 (20060101) |
Field of
Search: |
;524/464,469
;570/182,184,185,199,252,254 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1364397 |
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Aug 1974 |
|
GB |
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WO 91/19758 |
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Dec 1991 |
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WO |
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Other References
PCT/IL06/01327 Search Report dated Jun. 19, 2008. cited by
other.
|
Primary Examiner: Szekely; Peter
Attorney, Agent or Firm: Roach Brown McCarthy & Gruber,
P.C. McCarthy; Kevin D.
Claims
The invention claimed is:
1. Polybrominated bisaryl compounds containing
bromomethyl/bromomethylene groups according to the following
formula (I): ##STR00005## wherein a) Z is a bond, --O--,
--CH.sub.2--, --CH(CH.sub.3)--, --OCH.sub.2CH.sub.2O--, n=1-4,
p=1-4, m=1-4, and q=1-4; or b) Z is --CH(Br)--CH(Br)--, n=1-4,
p=1-4, m=0, and q=0.
2. Polybrominated bisaryl compounds according to claim 1 having a
formula selected from the group consisting of following formulae A
to F: ##STR00006## wherein X.sup.1, X.sup.2, X.sup.3, and X.sup.4
are independently selected from H and Br wherein at least one of
them is Br; ##STR00007##
3. A flameproof formulation comprising a polymeric material and at
least one of the polybrominated bisaryl compounds containing
bromomethyl/bromomethylene groups according to formula (I):
##STR00008## wherein a) z is a bond, --O--, --CH.sub.2--,
--CH(CH.sub.3)--, --OCH.sub.2CH.sub.2O--, n=1-4, p=1-4, m=1-4, and
q=1-4; or b) Z is --CH(Br)--CH(Br)--, n=1-4, p=1-4, m=0, and
q=0.
4. A flameproof formulation according to claim 3, wherein said
polybrominated bisaryl compounds have a formula selected from
formulae A to F: ##STR00009## wherein X.sup.1, X.sup.2, X.sup.3,
and X.sup.4 are independently selected from H and Br wherein at
least one of them is Br; ##STR00010##
5. A flameproof formulation according to claim 3, wherein said
polymeric material is selected from the group consisting of a
styrene-containing polymer, polystyrene, and foamed
polystyrene.
6. A flameproof formulation according to claim 5, wherein said
polystyrene is rated V-2 under UL-94 standard.
7. A flameproof formulation according to claim 3, further
comprising a synergist, said synergist being selected from the
group consisting of an organophosphorous compound, a flow-promoter
or a combination thereof.
8. A flameproof formulation according to claim 7, wherein the
organophosphorous compound is present in an amount of from about
0.5% to about 10% by weight, based on 100% of polymeric
material.
9. A flameproof formulation according to claim 7, wherein the
organophosphorous compound is triphenyl phosphate.
10. A flameproof formulation according to claim 7, wherein the flow
promoter is selected from the group consisting of
dimethyldiphenylbutane, dicumyl peroxide, or
.alpha.,.alpha.'-bis-tert-butylperoxydiisopropylbenzene,
diethyldiphenylbutane, and 2,3-dimethyl-2,3-diphenylbutane.
11. A flameproof formulation according to claim 10, wherein the
flow promoter is present in an amount of from about 0.01% to about
0.2% by weight based on 100% of polymeric material.
12. A flameproof formulation according to claim 10, wherein the
flow promoter is 2,3-dimethyl-2,3-diphenylbutane.
13. A flameproof formulation according to claim 5, wherein said
formulation is injection molded or compression molded.
14. A process for preparing a polybrominated bisaryl compound
containing bromomethyl/bromomethylene groups according to formula
(I): ##STR00011## wherein Z is a bond, --O--, --CH.sub.2--,
--CH(CH.sub.3)--, --OCH.sub.2CH.sub.2O--, n=1-4, p=1-4, m=1-4, and
q=1-4, said process comprising aromatic ring-bromination, followed
by benzylic bromination.
15. A process according to claim 14, wherein said bromomethyl
bisaryl compound has a formula selected from the group consisting
of formulae A to E: ##STR00012## wherein X.sup.1, X.sup.2, X.sup.3,
and X.sup.4 are independently H or Br wherein at least one of them
is Br; ##STR00013##
16. A process for preparing a polybrominated bisaryl compound
having formula F ##STR00014## said process comprising bromine
addition to the double bond of stilbene, and aromatic
ring-bromination.
17. A polybrominated compound according to claim 1, exhibiting a
weight loss of up to 10% at 270.degree. C.
18. A flameproof formulation according to claim 8, being
essentially transparent.
Description
FIELD OF THE INVENTION
The present invention relates to imparting flame-retardant
properties to styrene polymers, particularly to polystyrene
thermoplastic foams, via the incorporation of novel polybrominated
bisaryl compounds containing bromomethyl or bromomethylene
groups.
BACKGROUND OF THE INVENTION
Foamed polystyrenes are employed to an increasing extent in many
fields, above all in the building, construction and packaging
industries. In many cases it is desired to decrease the
flammability of such products by incorporating a flame retardant
into them.
It is common to use brominated aliphatics in the foamed polystyrene
industry, with hexabromocyclododecane (HBCD) being the most
commonly used flame retardant in foamed styrene polymers. The vapor
phase mode of action of brominated organic flame retardants relies
to a great extent on their thermal stability in relation to that of
the polymer. It is desirable to have a flame retardant compound
whose thermal stability is close to that of the polymer. This
mainly explains the high efficiency of the brominated aliphatics,
and among them HBCD, in imparting flame retardant properties to the
cellular and foamed polymer materials.
The process for the production of foamed polystyrene, especially
extruded polystyrene (XPS), is very sensitive to the quality of the
HBCD due to the relatively low thermal stability of HBCD and some
of the typical impurities in it. It is extremely important that the
flame retardant chosen for foamed polystyrene has good thermal
stability. Hydrogen bromide formed as a result of the thermal
decomposition of HBCD during the processing/foaming of polystyrene
will adversely affect the physical properties of the foamed polymer
product. In addition, the HBr formed may cause corrosion of the
metal equipment with which the hot blend comes into contact during
the process. Furthermore, the industry aims at increasing the
operating temperatures, for higher productivity of the process. In
order to suppress such undesirable, early, decomposition and to
optimize the performance, HBCD usually needs to be stabilized by
the addition of a variety of metal-organic and epoxy compounds, in
order to allow the processing of HBCD at higher temperatures and
for a longer period.
In view of the above, it can be seen that a need exists for
bromine-containing compounds which would be efficient fire
retardants for foamed polystyrenes while being more thermally
stable than HBCD and other known aliphatic bromine-containing
compounds both during the production of the foamed polystyrenes and
their processing and scrap recycling.
A Dow patent document, WO 91/19758, describes the limited fire
retardancy of HBCD, and discloses the use of a mixture of aliphatic
bromine compounds, especially HBCD and aromatic bromine compounds
such as decabromodiphenyl ether, as flame retardants for
polystyrene foams. Another Dow patent, U.S. Pat. No. 6,579,911,
discloses an application of HBCD, phosphorous compounds and flow
promoters, to improve the flame retardant efficiency of HBCD. The
patent emphasizes that, typically, only brominated aliphatic
compounds are utilized with styrene-based foams, with HBCD being
the most common.
US 2005/0043464 discloses topical application of brominated
aromatic compounds, used as additives to beads of polystyrene in a
process for making expanded polystyrene molded patterns in lost
foam aluminum castings. The brominated compounds accelerate
depolymerization of the polystyrene by the liberation of bromine
radicals, which reduce the viscosity of the liquid polystyrene.
U.S. Pat. Nos. 5,639,799 and 5,717,001 describe methods of
improving the thermal stability of HBCD for application in styrenic
polymer foam compositions.
It is, therefore, an object of the present invention to provide
novel bromine-containing fire retardants, which have both excellent
thermal stability and good fire-retardancy properties, particularly
when incorporated in foamed polystyrene.
It is another object of the present invention to provide such novel
fire retardants of suitable thermal stability against
dehydrobromination both during the production of the foamed
polystyrenes and their processing.
It is yet another object of the present invention to provide a
flameproof foamed polystyrene formulation, which contains such
bromine-containing fire retardants.
It is yet another object of the present invention to provide use of
the novel compounds of the invention and mixtures thereof, as
flame-retarding agents in polymeric materials, particularly in
foamed polystyrenes.
The present invention provides novel polybrominated bisaryl
compounds containing bromomethyl or bromomethylene groups which are
capable of imparting highly satisfactory flame-retarding qualities
to foamed polystyrenes, while being thermally stable against
dehydrobromination both during the production of the foamed
polystyrenes and their processing. The invention further provides
foamed polystyrene compositions containing the said novel
polybrominated bisaryl bromomethyl/bromomethylene compounds and
mixtures thereof that exhibit excellent fire retardancy.
Other objects and advantages of the invention will become apparent
as the description proceeds.
SUMMARY OF THE INVENTION
The present invention provides novel polybrominated bisaryl
compounds comprising bromomethyl or bromomethylene groups according
to the following formula (I):
##STR00001## wherein a) Z is a bond, --O--, --CH.sub.2--,
--CH(CH.sub.3)--, --OCH.sub.2CH.sub.2O--, m=1-4, n=1-4, p=1-4, and
q=1-4; or b) Z is --CH(Br)--CH(Br)--, n=1-4, p=1-4, m=0, and
q=0.
Preferred compounds according to formula (I) of the present
invention have a formula selected from the following group
consisting of formulae A to F:
##STR00002## wherein X.sup.1, X.sup.2, X.sup.3, and X.sup.4 are
independently H or Br wherein at least one of them is Br;
##STR00003##
The present invention also provides processes for the preparation
of the said novel compounds by bromination of the corresponding
bisaryl compounds.
The polybrominated bisaryl compounds of this invention possess
excellent thermal stability and are useful as flame retardants in
styrene-containing polymers, preferably in polystyrene, and most
preferably in foamed polystyrene. The present invention further
provides fire retarded foamed polystyrene compositions comprising
said novel polybrominated bisaryl compounds, and mixtures thereof,
as flame retarding agents. All the above and other characteristics
and advantages of the invention will be better understood through
the following illustrative and non-limitative detailed description
of the preferred embodiments thereof.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
It is an object of the present invention to provide a group of
novel polybrominated bisaryl compounds containing bromomethyl or
bromoethylene groups. The preparation of the novel compounds of
formulae A to F of the invention comprises aromatic
ring-bromination, and, except for compound of formula F, radical
bromination to produce bromomethyl groups. The bromomethyl groups
in the compound of formula F result from a bromine addition
reaction to a double bond of stilbene.
Aromatic Ring-Bromination
The aromatic bromination is carried out in a suitable organic
solvent. or in bromine as a solvent. Halogenated lower alkanes of
1-6 carbon atoms free of carbon to carbon unsaturation are suitable
for this purpose. Specific useful solvents include carbon
tetrachloride, chloroform, dichloroethane, tetrachloroethane,
methylene chloride, dibromomethane and bromochloromethane, or
mixtures thereof. Preferably, the solvent is substantially
anhydrous. Water destroys the catalyst and causes the reaction to
proceed at a slower rate. As used here, the term "solvent" includes
one of the reactants itself which has the described requirements of
the solvent. For example, bromine in excess can itself serve as the
solvent.
The aromatic bromination is performed in the presence of a Lewis
acid catalyst, and optionally for some of the bisaryl substrates
(compounds of formulae C and D) no catalyst is needed to achieve
the necessary degree of bromination.
The most desirable Lewis acid catalysts are those metal halides
capable of effecting a Friedel-Crafts reaction. Of these, the
preferred ones are the bromides and chlorides of aluminium and
antimony. However, metals such as Fe and Sn, or metal oxides, for
example antimony oxide, are not excluded from the scope of the
present invention, and may also be used as catalysts according to
the present invention. An amount of the catalyst is used which can
be readily determined by routine experiment. In general, the amount
of catalyst used may range from 5% to 25%, and preferably from 10%
to 22%, by weight of the bisaryl substrate.
Any stoichiometric excess of bromine over the bisaryl substrate is
effective to encourage complete aromatic ring-bromination within a
reasonable period of time. Generally, the excess of bromine to the
bisaryl compound to be fully brominated is at least 5% molar. As
said above, bromine can optionally be used as the solvent. The rate
of adding the bromine is not critical as long as a stoichiometric
excess is present at least at the end of the reaction to encourage
as complete a bromination as possible. As an example, a
stoichiometric excess of bromine can be added to the bisaryl
substrate over a period of time from about 30 min to 3 hours.
Bromine chloride, by which a mixture of bromine and chlorine is
meant, may also be used as a brominating agent for the aromatic
bromination in the process of the present invention. Bromine and
chlorine are generally used in a molar ratio of from (0.7-1.3):1,
and preferably bromine and chlorine are used in about a 1:1 molar
ratio. Generally, the excess of bromine chloride to the bisaryl
substrate is at least 5% molar.
The temperature of the process is preferably from 0.degree. C. up
to about 80.degree. C. The reaction is usually completed within
about two to ten hours, depending on the conditions and
reactants.
The final reaction mixture is treated by adding successively water
and a reducing agent such as sodium bisulfite, sodium sulfite or
hydrazine. The water destroys and removes the catalyst. The
reducing agent neutralizes the excess bromine (in the case of the
compound of formula F after the distillation of most of the
bromine).
In one mode suitable for the purpose of the present invention,
successive aromatic and benzylic brominations of the brominated
product are carried out by isolating the aromatic brominated
product prior to the benzylic bromination
In another suitable mode, both aromatic and benzylic bromination
are carried out as a one-pot two-stage process without isolating
the intermediate polybrominated bisaryl compound.
Benzylic Bromination
The second chemical stage (for compounds of formulae A to E) is a
selective monobromination of the methyl group (also known as
benzylic bromination) in the intermediate products isolated after
the aromatic bromination. This is achieved by a radical process,
using some source of radical initiator to convert the bromine
molecule into reactive radicals which attack the methyl group to
form the bromomethyl functionality. The choice of radical source is
rather limited while the influence of the initiator on the final
purity of the product is significant
One of the most suitable radical initiators for this purpose is
2,2'-azobisisobutyronitrile (AIBN). The decomposition of AIBN is
essential for the benzylic bromination to proceed since the
radicals formed by the decomposition of the AIBN initiate the
formation of bromine radicals which are the active brominating
species in this type of reaction. It is highly recommended that
such reactions be performed at temperatures that will ensure a high
selectivity together with a reasonable reaction time. At a too low
temperature the formation of the radicals will be slowed down so
that no effective reaction will occur. The temperature of the
process is preferably from 60.degree. C. up to 80.degree. C., with
temperatures from about 69.degree. C. to about 75.degree. C. being
most preferred. Photochemical reaction can also be a source for Br
radicals.
The benzylic bromination is preferably carried out in a halogenated
organic solvent which boils in this range of temperatures. A
mixture of dichloromethane, bromochloromethane and dibromomethane
in a ratio of 10:20:70 wt. meeting such a requirement is the most
preferred. An effective amount of the AIBN employed in the benzylic
bromination is in a range of 5 to 50% by weight, and preferably 10
to 40% by weight to the amount of the ring-brominated intermediate
substrate.
The presence of an appropriate amount of water is essential for a
high benzylic bromination efficiency. A stoichiometric excess of
bromine in a range of 1.1 mol to 2 mol per methyl group, and
preferably in a range of 1.2 to 1.8 mol bromine per methyl group,
in the ring-brominated intermediates is effective in achieving
complete benzylic bromination within a reasonable period of
time.
The final reaction mixture is treated by the addition of a reducing
agent such as sodium bisulfite, sodium sulfite or hydrazine to
neutralize the excess bromine.
The following examples illustrate specific embodiments of both the
preparation of the novel polybrominated bisaryl compounds of the
invention and the utility of these compounds as flame retardants in
foamed polystyrenes. The following examples should not be construed
as limiting the scope of the invention.
EXAMPLE 1
Preparation of the Compound of Formula A
A 1 liter jacketed reactor, equipped with a mechanical stirrer, a
thermocouple and a reflux condenser, was charged with a solvent
mixture of dichloromethane, bromochloromethane and dibromomethane
(20:40:40 wt., 500 g), AlCl.sub.3 (5 g) and p-tolyl ether (50 g).
The temperature was set at 20.degree. C., then bromine (350 g) was
fed in via a peristaltic pump at a rate of 3 g/min. A post-reaction
of 2.5 hours at reflux brought the reaction to completion
(confirmed by GC analysis).
Work-up and isolation of the crude octabromodimethyldiphenyl ether
was performed by adding water (100 g) and aq. 17% hydrazine (30 g)
to the reaction mixture for catalyst destruction and reduction of
excess bromine. The aqueous layer was separated. The organic slurry
was mixed with water (100 g), filtered, and washed with solvent
mixture (57 g) and water (100 g).
After vacuum drying there was obtained 196 g of
octabromo-dimethyldiphenyl ether (93% of the theoretical, based on
p-tolyl ether).
A mixture of bromochloromethane and dibromomethane (20:80 wt., 500
g), octabromodimethyldiphenyl ether (185 g), bromine (107 g) and
water (107 g) were introduced into the reactor. The mixture was
heated to 69.degree. C., and azobis-isobutyronitrile (AIBN) was
added in small portions (8.times.2 g) over 5 hours.
The reaction mixture was cooled to 40.degree. C. and the excess
bromine was neutralized with aq. 17% hydrazine (25 g). The aqueous
phase was separated. The organic slurry was mixed with water (120
g), filtered, and washed with solvent mixture (50 g) and water (125
g). After vacuum drying there was obtained 206 g (94% of the
theoretical, based on octabromodimethyldiphenyl ether) of pure
1,1'-oxybis(4-bromomethyl-2,3,5,6-tetrabromo)benzene (compound A,
confirmed by HPLC/MS, H.sup.1-NMR) in the form of a white powder,
melting point 266-268.degree. C., % Br calculated: 81.0%, found:
81.7% benzylic Br calculated: 16.2%, found 16.4%. Differential
scanning calorimetry (DSC) analysis showed the purity to be 99%.
Thermogravimetric analysis (TGA): 5 and 10% weight loss at
346.degree. C. and 359.degree. C., respectively.
EXAMPLE 2
Preparation of the Compound of Formula B
A 0.5 liter jacketed reactor, equipped with a mechanical stirrer, a
thermocouple and a reflux condenser, was charged with a solvent
mixture of dichloromethane, bromochloromethane and dibromomethane
(20:40:40 wt., 150 g), AlCl.sub.3 (2 g) and 4,4'-dimethylbiphenyl
(9.1 g). The temperature was set at 25.degree. C., and then bromine
(70 g) was fed in over a period of 1.5 hour. A post-reaction of
four hours at reflux brought the reaction to completion (confirmed
by GC analysis).
Work-up and isolation of the crude octabromodimethylbiphenyl was
performed by adding water (75 g) and aq. 17% hydrazine (8 g) to the
reaction mixture for catalyst destruction and reduction of excess
bromine. The aqueous layer was separated. The organic slurry was
mixed with water (50 g), filtered, and washed with solvent mixture
(20 g) and water (70 g).
After vacuum drying there was obtained 31.5 g of
octabromodimethylbiphenyl (77% of the theoretical, based on
4,4'-dimethylbiphenyl).
A mixture of bromochloromethane and dibromomethane (15:85 wt., 140
g), octabromodimethylbiphenyl (26 g), bromine (18 g) and water (25
g) were introduced into the reactor. The mixture was heated to
72-75.degree. C., and AIBN was added in small portions (5.times.2
g) over 5 hours.
The reaction mixture was cooled to 40.degree. C. and the excess
bromine was neutralized with aq. 17% hydrazine (4 g). The aqueous
phase was separated. The organic slurry was mixed with water (50
g), filtered, and washed with solvent mixture (10 g) and water (25
g). After vacuum drying there was obtained 22 g (71% of the
theoretical, based on octabromodimethylbiphenyl) of pure
4,4'-bisbromomethyl-octabromo-biphenyl (compound B, confirmed by
HPLC/MS, .sup.1H-NMR) in the form of a white powder, melting point
320-322.degree. C., % Br calculated: 82.3%, found: 82.6% benzylic
Br calculated: 16.5%, found 16.7%. TGA: 5 and 10% weight loss at
325 and 339.degree. C.
EXAMPLE 3
Preparation of the Compound of Formula C
A 0.5 liter jacketed reactor, equipped with a mechanical stirrer, a
thermocouple and a reflux condenser, was charged with a solvent
mixture of dichloromethane, bromochloromethane and dibromomethane
(20:40:40 wt., 100 g) and bromine (145 g). The temperature was set
at 25.degree. C., then a solution of bismesityl methane (38 g) in
solvent mixture (200 g) was fed in over a period of 1.5 hours. A
post-reaction of two hours at 25.degree. C. brought the reaction to
completion (confirmed by GC analysis).
Work-up and isolation of the crude
bis(3,5-dibromo-2,4,6-trimethyl)methane was performed by adding
water (100 g) and aq. 37% NaHSO.sub.3 (110 g) to the reaction
mixture for reduction of excess bromine. The aqueous layer was
separated. The organic slurry was filtered, and washed with solvent
mixture (40 g) and water (55 g).
After vacuum drying there was obtained 72 g of
bis(3,5-dibromo-2,4,6-trimethyl)methane (84% of the theoretical,
based on bismesityl methane), melting point 284-287.degree. C.
A mixture of bromochloromethane and dibromomethane (25:75 wt., 80
g), bis (3,5-dibromo-2,4,6-trimethyl)methane (17 g), bromine (40 g)
and water (40 g) were introduced into the reactor. The mixture was
heated to 74-76.degree. C., and AIBN was added in small portions
(6.times.0.5 g) over 7 hours.
The reaction mixture was cooled to 40.degree. C. and the excess
bromine was neutralized with aq. 37% NaHSO.sub.3 (8 g). The aqueous
phase was separated. The organic solution was washed with water (40
g), followed by phase separation and stripping of about half of the
solvent mixture. The precipitate was filtered, and washed with
dichloromethane (10 g) and water (30 g). After vacuum drying there
was obtained 20 g (64% of the theoretical, based on
bis((3,5-dibromo-2,4,6-trimethyl)methane), of
bis(3,5-dibromo-2,4,6-tribromomethylphenyl)methane (compound C,
confirmed by HPLC/MS, .sup.1H-NMR) in the form of a white powder,
melting point 214-216.degree. C., % Br calculated: 76.8%, found:
74.8%, benzylic Br calculated: 46.1%, found 44.8%. TGA: 5 and 10%
weight loss at 271.degree. C. and 284.degree. C.
EXAMPLE 4
Preparation of the Compounds of Formula D
A 1 liter jacketed reactor, equipped with a mechanical stirrer, a
thermocouple, and a reflux condenser, was charged with a solvent
mixture of dichloromethane, bromochloromethane and dibromomethane
(20:40:40 wt., 350 g) and bromine (350 g). The temperature was set
at 24.degree. C., then 1,1-bis(3,4-dimethylphenyl)ethane (83 g) was
fed in over a period of 2 hours. A post-reaction of three hours at
40.degree. C. brought the reaction to completion (confirmed by GC
analysis).
Work-up and isolation of the mixture of
1-(dibromodimethyl-phenyl)-1-(dibromodimethyl-phenyl)ethanes was
performed by adding water (50 g) and aq. 37% sodium bisulfite (208
g) to the reaction mixture for reduction of excess bromine. The
aqueous layer was separated. The organic slurry was mixed with
solvent mixture, filtered, and washed with solvent mixture and
water. After vacuum drying there was obtained 178 g (92% of the
theoretical, based on 1,1-bis(3,4-dimethylphenyl)ethane) of an
mixture of
1-(dibromodimethylphenyl)-1-(dibromodimethylphenyl)ethanes, melting
point 222-224.degree. C.
A mixture of bromochloromethane and dibromomethane (25:75 wt., 150
g), mixture of
1-(dibromodimethylphenyl)-1-(dibromodimethylphenyl)ethanes (55 g),
bromine (80 g) and water (80 g) were introduced into the reactor.
The mixture was heated to 74-76.degree. C., and AIBN was added in
small portions (6.times.1 g) over 5 hours. The reaction mixture was
cooled to 40.degree. C. and the excess bromine was neutralized with
aq. 37% sodium bisulfite (8 g). The aqueous phase was separated.
The organic phase was washed with water (60 g), followed by partial
evaporation of the solvent. After cooling to 5.degree. C. the
precipitate formed was filtered, and washed with dichloromethane
(33 g) and water (50 g). After vacuum drying there was obtained 18
g (about 20% of the theoretical, based on
1,1-bis((dibromodimethylphenyl)ethane), of a mixture of brominated
(at three methyl groups on the benzene rings)
1-(tribromobromomethyl
methylphenyl)-1-(tribromodimethylphenyl)ethanes (compounds of
formula D, confirmed by HPLC/MS) in the form of a white powder,
melting point 191-195.degree. C., % Br calculated: 77.8%, found:
78.1%, benzylic Br calculated: 31.1%, found 24.6%. TGA: 5 and 10%
weight loss at 274 and 290.degree. C.
EXAMPLE 5
Preparation of the Compounds of Formula E
A 2 liter reactor, equipped with a mechanical stirrer, a
thermocouple and a reflux condenser, was charged with
dichloroethane (1120 g), bis(3-methylphenoxy)ethane (40 g) and
antimony oxide Sb.sub.2O.sub.3 (6.6 g). Bromine (316.4 g) was fed
in via a peristaltic pump over 1 hour at room temperature. After
the addition of half the amount of bromine, the reaction mixture
was heated to 40.degree. C. After the bromine addition was
completed the reaction mixture was heated at 75-77.degree. C. over
a period of 8 hours. The reaction mixture was cooled to room
temperature, water (100 g) was added, then aq. 37% sodium bisulfite
was added for catalyst destruction and reduction of excess bromine.
The solid was filtered and washed with dichloroethane, then with 5%
sodium bicarbonate solution and water. After vacuum drying there
was obtained 102.7 g of
1-(tribromo-3-methylphenoxy)-2-(tribromo-3-methylphenoxy)ethanes
(87% of the theoretical, based on bis(3-methylphenoxy)ethane),
melting point 242-244.degree. C. GC analysis showed the purity to
be above 98% (area %).
A mixture of dichloro-, bromochloro- and dibromomethane (10:20:70
wt., 2100 g),
1-(tribromo-3-methylphenoxy)-2-(tribromo-3-methyl-phenoxy)-ethan-
es (96 g), bromine (60 g) and water (100 g) were introduced into
the reactor. The mixture was heated to 70-73.degree. C. AIBN (5 g)
was added to the mixture in five portions, 1 hour between each
portion. The reaction mixture was cooled to 25.degree. C. The
bromine excess was reduced with aq. 37% sodium bisulfite solution.
The organic mixture was washed with water and neutralized with aq.
5% sodium bicarbonate solution. The precipitate was filtered and
washed with dichloromethane and water. After vacuum drying there
was obtained 111.6 g (95% of the theoretical, based on
1-(tribromo-3-methylphenoxy)-2-(tribromo-3-methyl-phenoxy) of pure
1-(tribromo-3-bromomethylphenoxy)-2-(tribromo-3-bromomethylphenoxy)ethane-
s (compounds of formula E, confirmed by HPLC/MS, .sup.1H-NMR) in
the form of a white powder, melting point 238-240.degree. C., % Br
calculated: 73.2, found: 73.1, % benzylic Br calculated: 18.3,
found 18.0. HPLC analysis showed the purity to be above 99.5% (area
%). NMR suggested that most of the material is represented by a
symmetric formula of bis(tribromo-3-bromomethylphenoxy)ethane. TGA:
5 and 10% weight loss at 294.degree. C. and 300.degree. C.
EXAMPLE 6
Preparation of the Compound of Formula F
Two-Step Process
A 1 liter jacketed reactor, equipped with a mechanical stirrer, a
thermocouple and a reflux condenser, was charged with
dichloromethane (520 g) and trans-stilbene (54 g), followed by the
addition of bromine (50 g). After 1 h stirring at room temperature,
200 ml of water was introduced into the reactor and the excess
bromine was neutralized with aq. 37% sodium bisulfite. The organic
solvent was then distilled. The obtained slurry was filtered to
give 98.2 g (96.3% of the theoretical, based on trans-stilbene) of
1,2-dibromo-1,2-diphenylethane as a pale yellow solid.
A 0.5 liter jacketed reactor equipped with a mechanical stirrer, a
thermometer and a reflux condenser was charged with bromine (310
g), 1,2-dibromo-1,2-diphenylethane (20.4 g) and AlCl.sub.3 (2 g).
The reaction was slightly exothermic. The reaction mixture was
stirred until no more HBr was evolved. Water (100 g) was added
dropwise and the mixture was heated to 60.degree. C. for the
distillation of the major part of unreacted bromine. The obtained
slurry was treated with aq. 37% sodium bisulfite, filtered and
washed with water. The filtered powder was poured into xylene (200
ml) and aq. 37% sodium bisulfite (60 g) and heated to 70.degree. C.
for 4 h. After filtration, washing with water and vacuum drying,
there was obtained 52 g (90% of the theoretical based on
1,2-dibromo-1,2-diphenylethane) of
1,2-dibromo-1,2-bis(2,3,4,5-tetrabromophenyl)ethane (compound of
formula F, confirmed by, X-Ray) in the form of a white solid,
melting point 282-283.degree. C., % Br calculated: 82.2%, found:
80.5%. TGA: 5 and 10% weight loss at 291 and 295.degree. C.
One-Step Process
A 0.5 liter jacketed reactor, equipped with a mechanical stirrer, a
thermometer and a reflux condenser, was charged with bromine (750
g), trans-stilbene (21.6 g) and AlCl.sub.3 (4.2 g). The reaction
mixture was stirred until no more HBr evolved. Work-up and
isolation of the product was performed as described for the
two-step process. After vacuum drying there was obtained 107 g (92%
of the theoretical, based on trans-stilbene) of
1,2-dibromo-1,2-bis(2,3,4,5-tetrabromophenyl)ethane (compound of
formula F).
Besides the novel brominated flame-retarding agents of the present
invention, the flame-retarding compositions, prepared according to
the method of the present invention, may incorporate other
additives as processing aids, synergists, and flow-promoters,
aiding in imparting flame-retardant qualities to the host polymer
material. Thus, U.S. Pat. No. 6,579,911 describes mixtures of
polystyrenes, phosphorous compounds and flow promoters. Preferably,
the synergist is an organophosphorous compound, including
phosphates, phosphonates, phosphinates, phosphites and phosphine
oxides. Particularly, such organophosphorous synergists may be of a
monomeric, dimeric or oligomeric type, and may contain aromatic
moieties.
Particularly suitable organophosphorous synergists having aromatic
moieties include aromatic phosphate esters, represented by formula
(II):
##STR00004## in which R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are
aryl groups, which may be the same or different, A is an arylene
group, and `n` is an integer from 0 to 5. The phosphate esters can
be either triarylphosphates, where `n` in the formula given above
is 0, or monomeric bisphosphates, where `n` in the formula is 1, or
mixtures of said triaryl phosphates and monomeric bisphosphates
with higher oligomers, where `n` for each oligomer is an integer
from 2 to 5 (said mixtures hereinafter indicated also as oligomeric
phosphates).
The aryl group may be phenyl, cresyl, 2,6-xylenyl, and the like.
The arylene group may be a group derived from a dihydric compound,
for example, resorcinol, bisphenol-A, 4,4'-biphenol, and the like.
Especially preferred arylphosphate esters for use herein include
triphenyl phosphate (TPP) and phenylphosphate esters of
4,4'-biphenol. Preferably, the phosphorous synergists may consist
of a single phosphorus-containing material or they may consist of a
mixture of two or more different organic phosphorus-containing
compounds, which may be suitable for obtaining the desired
properties of the polystyrene foam.
The phosphorous synergist may typically, although non-limitatively,
be present in amounts ranging from about 0.1% to about 10.0% by
weight based on 100% of the styrene polymer. Most preferably, the
amount of phosphorous synergist in the composition ranges from
about 0.5% to about 2.0% by weight based on 100% of the styrene
polymer. The flame-retarding composition, containing an
organophosphorous flame-retardant as synergist, can be used either
as a viscous liquid or more preferably as solid flakes (TPP) or as
a preliminary melt mixed in the polystyrene polymer.
In another preferred embodiment of the present invention flow
promoters are selected from dimethyldiphenylbutane, dicumyl
peroxide or
.alpha.,.alpha.'-bis-tert-butylperoxydiisopropylbenzene, and
diethyldiphenylbutane, in typical amounts of between about 0.01%
and about 0.2% by weight based on 100% of styrene polymer. More
preferably, the amounts range from about 0.02% to about 0.1% by
weight based on 100% of styrene polymer. An illustrative example of
a flow-promoter is dicumyl (2,3-dimethyl-2,3-diphenylbutane).
Process Background and Experimental Conditions
Test Methods
It is well known that the performance of injection molded and
compression molded flame retarded polystyrene measured by LOI and
UL-94 can be taken as indicative of the performance of flame
retardant additives in foamed polystyrene.
Therefore, injection molded and compression molded specimens were
used to exemplify the efficiency of the novel polybrominated
bisaryl compounds of the invention, as flame retardants in
polystyrene. For this purpose injection molded or compression
molded specimens were prepared and their flame retardancy measured
by the methods detailed in Table 1.
TABLE-US-00001 TABLE 1 Test methods, Standard flammability test
methods for compression molded and injection molded polystyrene
PROPERTY METHOD APPARATUS LOI ASTM D 2863-77. Measuring Stanton
Redcroft FTA (Limiting Oxygen the minimum oxygen Flammability Unit.
Index) concentration to support candle-like combustion of plastics.
Flammability UL-94 Vertical burning test Hood and burner as at 3.2
mm (Underwriter specified by UL Laboratories)
Compounding
All the components (plastic pellets and powders) were weighed on
Sartorius semi-analytical scale with subsequent manual mixing in a
plastic bag. Formulations were compounded in a Berstorff twin-screw
extruder Type ZE-25, L/D=32:1 fed from one feeder. The compounding
conditions are presented in Table 2. The obtained strands were
cooled in a water bath and then pelletized in the Pelletizer 750/3
ex. Accrapak Systems Limited. The obtained pellets were dried in a
circulating air oven at 70.degree. C. for two hours.
Injection Molding
The compounded pellets were molded using an Arburg-Allrounder
machine model 320s/500-150. LOI and UL test specimens were molded
using a no. S 22963 mold. The molding conditions are presented in
Table 3.
TABLE-US-00002 TABLE 2 Regime of compounding in co-rotating
twin-screw extruder ex Berstorff ACTUAL PARAMETER UNITS SET VALUES
VALUES T.sub.1 Feeding zone .degree. C. no heating T.sub.2 .degree.
C. 140 142 T.sub.3 .degree. C. 150 154 T.sub.4 .degree. C. 170 186
T.sub.5 .degree. C. 170 188 T.sub.6 .degree. C. 180 196 T.sub.7
vent .degree. C. 180 200 T.sub.8 .degree. C. 180 195 T.sub.9 nozzle
.degree. C. 190 201 Melt temperature .degree. C. 203 Screw speed
RPM 375 375 Ampere A 11-12 Feeding rate kg/hour 11.8 11.8
TABLE-US-00003 TABLE 3 Regime of injection molding PARAMETER UNITS
VALUES T.sub.1 (Feeding zone) .degree. C. 160 T.sub.2 .degree. C.
180 T.sub.3 .degree. C. 180 T.sub.4 .degree. C. 180 T.sub.5
(nozzle) .degree. C. 180 Mold temperature .degree. C. 40 Injection
pressure bar 900 Holding pressure bar 700 Back pressure bar 0
Injection time sec 0.1 Holding time sec 2 Cooling time sec 10 Mold
closing force kN 131 Filling volume (portion) cc 37 Injection speed
cc/sec 20
Compression Molding
All the components (plastic pellets and powders) were weighed on
Sartorius semi-analytical scale with subsequent manual mixing. 70
gr of the mixture was compounded in a Brabender Plasticorder cell
at 200.degree. C. for 8 min and air cooled to 160.degree. C. The
compounding speed was 40 RPM.
Test plates of 127.times.6.5.times.3.2 mm were prepared by pressing
the compounded mixture in a press type Polystat ex. Schuabenthan at
the following setting: Press conditions: Temperature 180.degree.
C., first pressure 1 min, 0 bar, second pressure 1 min, 100
bar.
The pressed plates were cooled to 100.degree. C. with running water
and the samples were removed from the press. The plates were cut to
LOI test specimens 6.5.times.127.times.3.2 mm. The test specimens
were conditioned for 48 hours at ambient conditions before
flammability tests.
Materials
Polystyrene used in the following examples was commercial
polystyrene type 637 (ex Dow). Triphenyl phosphate, Reomol (ex Ciba
Geigy) was used as a commercial example of the phosphate ester.
The flow promoter used was commercial Interox C-C DFB Peroxide
Chemie; 2,3-dimethyl-2,3-diphenyl butane, also referred to as
dicumyl.
Flame retardants of the present invention--novel brominated bisaryl
compounds containing bromomethyl/bromomethylene groups--were
selected from the group consisting of the compound of formula A,
the compound of formula B, the compound of formula C, a compound of
formula D or a mixture of compounds of formula D, a compound of
formula E or a mixture of compounds of formula E, and the compound
of formula F, which formulae A to F are described above.
The aforesaid and other characteristics and advantages of the
invention will be better understood through the description of the
following illustrative and non-limitative examples demonstrating
the utility of the polybrominated bisaryl compounds of the
invention as flame retardants in foamed polystyrenes.
EXAMPLES 7-13
Compression Molding
Polystyrene compression molding specimens 7-13, the compositions of
which are detailed in Table 4, were compounded and molded
substantially according to the procedures described above.
Flammability testing of compression molded formulations 7-13 was
conducted under standard LOI (Limiting Oxygen Index) testing, to
which reference is made in Table 1.
Table 4 details the formulations, differing in the brominated
bisaryl compound of the invention employed as flame retardant, with
one formulation containing HBCD for reference. The flammability
results of these compression-molded flame-retarded polystyrene
specimens, measured according to the LOI standard procedure, are
summarized in Table 4. The results clearly demonstrate that
compression molded specimens can be used for evaluating the flame
retardant performance of the products of the invention.
Polybrominated bisaryl compounds containing bromomethyl groups pass
the required levels.
TABLE-US-00004 TABLE 4 Composition and flammability of compression
molded FR-PS test pieces % Br in Example formulation Trans- No.
Br-FR type % Br-FR (calculated) LOI parency 7 HBCD 2.74 2.0 23.5
Yes 8 Compound A 2.5 2.0 23.3 Yes 9 Compound B 2.4 2.0 22.7 Yes 10
Compound C 2.7 2.0 24.6 Yes 11 Compounds D 2.6 2.0 25.7 Yes 12
Compounds E 2.7 2.0 24.3 Yes 13 Compound F 2.5 2.0 24.7 Yes
Table 4 shows that the efficiency of different polybrominated
bisaryl compounds of the present invention as flame retardants for
polystyrene is satisfactory, all behave in a similar way and are as
efficient as HBCD. All the compression molded FR test pieces had
good transparency. This indicates that the compounds of the
invention are well compatible with the polystyrene.
EXAMPLES 14-19
Injection Molding
Polystyrene injection molding specimens 14-19, the compositions of
which are detailed in Table 5, were compounded and injection molded
substantially according to the compounding and injection molding
procedures described above. Their regimes are detailed in Tables 2
and 3, respectively.
The flammability testing of injection molded formulations 14-19
described in Table 5, was conducted under the standard LOI
(Limiting Oxygen Index) and UL 94 tests, to which reference is made
in Table 1.
Table 5 details the different formulation components used for
injection-molded specimens 14-19. The formulations contain
polybrominated stilbene (compound of formula F) in different
relative amounts, with or without the addition of a
phosphorus-containing flame retardant synergist and dicumyl
flow-promoter. One formulation contains HBCD for reference. The
flammability results of these injection-molded flame-retarded
polystyrene specimens, measured according to LOI and UL-94 standard
procedures, are summarized in Table 5.
As mentioned above, injection-molded specimens can be used for
evaluating the flame retardant performance of flame retardant
products. According to the results in Table 5, polybrominated
bisaryl compound F of the invention has an LOI value higher than
that for HBCD. The data in Table 5 clearly demonstrates the
advantage of employing synergists in the formulations. In all such
formulations, the LOI is higher than in formulations that did not
contain synergists.
TABLE-US-00005 TABLE 5 Composition and flammability of injection
molded FR-PS test pieces % Br in % P in % Interox Exp. Br-FR % Br-
formulation P-FR formulation CC DFB in UL-94 No. type FR
(calculated) (% P-FR) (calculated) formulation LOI at 3.2 mm
Transparency 14 HBCD 2.7 2 -- -- -- 23.1 V-2 Yes 15 Comp. F 2.9 2.0
-- -- -- 25.0 V-2 Partial 16 Comp. F 2.1 1.5 -- -- -- 24.3 V-2 Yes
17 Comp. F 1.4 1.0 -- -- -- 22.3 V-2 Yes 18 Comp. F 2.1 1.5 TPP
(1%) 0.095 0.1 27.5 V-2 Yes 19 Comp. F 2.1 1.5 TPP (3%) 0.29 0.4
29.1 V-2 Yes *TPP--Triphenyl phosphate
While examples of the invention have been described for purposes of
illustration, it will be apparent that many modifications,
variations and adaptations can be carried out by persons skilled in
the art, without exceeding the scope of the claims.
* * * * *